地形强迫对大气长波调整的可能影响

地形作为大气的外部强迫，其动力和热力作用对波动结构演变及极端天气出现都有不能忽视的作用。本文通过数值求解考虑地形强迫的β平面正压准地转位势涡度方程，探讨了地形强迫作用对大气长波调整的可能影响，结果表明:同非线性作用和纬向非均匀基流作用一样，无基流情形下具有纬向差异的地形分布影响了大气长波结构的演变，也能强迫出大气长波调整现象。大气长波调整依赖于地形的高度和地形分布，地形越高，长波越容易出现波数的调整；地形波数越大，即地形结构复杂，越不易出现波数变化。大气长波调整还与纬度有关，纬度越高，β越小，地形强迫作用越突出，长波调整容易出现；反之，低纬度以β效应为主的线性波动不易出现波数调整。大气长波调整对波动初始波动的振幅不敏感，但依赖于波动的初始结构。此外，有基流作用时，地形强迫还是诱发定常波的重要因素，且定常波流场结构依赖于地形高度分布，与波动初始结构无关。

Possible Impacts of Topography on Adjustment of Atmospheric Long-Waves

Topography is an important external forcing factor on the atmosphere and has orographic thermal and dynamic impacts on the evolution of atmospheric long waves and the emergence of extreme weather. In this study, numerical calculation with the forced β plane quasi-geostrophic potential vorticity equation considering linear Rossby waves with and without the influence of basic flow is used to investigate the possible impacts of topography on the adjustment of long waves. The results show that without the basic flow, the phenomenon of long-wave adjustment was accompanied by the forcing of zonal nonuniform topography, which is also an important mechanism for the adjustment. The adjustment is closely related to topographic amplitude and zonal structure. As the amplitude of topography increases, the phenomenon of wave-number adjustment in the evolution of linear Rossby waves becomes more obvious. However, the adjustment is difficult to identify in topography with a high zonal wave number. Long-wave adjustment is also associated with latitude. High latitude relates to a low β value in which the influence of topography is strong and adjustment of the wave number is simple. On the contrary, the wave number of a linear Rossby wave with a large β effect in low latitudes is not easily changed. Long-wave adjustment is associated with the structure of the initial field and is not sensitive to the amplitude of the initial fluctuation. Moreover, when the basic flow is considered, the forcing of topography is also an important factor in producing a solitary Rossby wave. The structure of this solitary wave is determined by the distribution of the topography and is independent of the structure of initial fluctuation.